This invention concerns apparatus for processing the side panel chrominance information of a widescreen television-type signal having an image aspect ratio, e.g., 16.times.9, greater than that of a standard television image.
A conventional television receiver, such as a receiver in accordance with the NTSC broadcast standard adopted in the United States and elsewhere, has a 4:3 aspect ratio (the ratio of the width to the height of a displayed image). Recently, there has been interest in using higher aspect ratios for television systems, such as 2:1, 5:3 or 16:9, since such higher aspect ratios more nearly approximate or equal the aspect ratio of the human eye than does the 4:3 aspect ratio of a standard television receiver display.
It is desirable for widescreen television systems to be compatible with standard television receivers to facilitate the widespread adoption of widescreen systems. One known compatible widescreen television system is described by M. A. Isnardi et al. in an article "Encoding for Compatibility and Recoverability in the ACTV System", published in IEEE Transactions on Broadcasting, Vol. BC-33, December 1987and in U.S. Pat. No. 4,855,811 of M. A. Isnardi. This known system includes apparatus designed for processing a widescreen video signal representing a 5.times.3 aspect ratio image to develop a compatible widescreen television signal which produces a standard 4.times.3 aspect ratio display when received by a conventional television receiver, and which produces a widescreen 5.times.3 aspect ratio display when received by a widescreen television receiver. In this known system, low frequency side panel information is time compressed 6:1 (resulting in a proportional increase in frequency) and placed in the horizontal overscan regions of the center panel information component. High frequency side panel information is time expanded about 1:4.4 (resulting in a proportional decrease in frequency) before modulating a 3.1 MHz auxiliary subcarrier having a field alternating phase, forming a double sideband auxiliary signal which is combined with the main panel signal before being transmitted. To assist a decoder in recovering the center and side panel components at a widescreen receiver, the side panel and center panel luminance components are intraframe averaged above 700 KHz and 1.5 MHz respectively before modulation and combination at the transmitter.